Experimental Study On Prevention And Control Of Coal Spontaneous Combustion By Liquid CO₂

China is rich in coal resources,production and consumption rank the forefront of the world.However,in the process of coal mining,coal spontaneous combustion has become one of the main factors restricting the safe production and development of mine.As a spontaneous combustion control technology of coal mine,the use of liquid CO₂ for spontaneous combustion of coal seam has the advantages of good cooling effect,large inerting range,long acting time,safe and reliable,simple operation and so on.Therefore,it is widely concerned by coal mine safety workers.In this paper,through the combination of theoretical analysis and experimental research,the experiment system of cooling and discharging liquid CO₂ is designed and built,and the process and law of liquid CO₂ cooling are studied.Firstly,in the large cooling experiment The temperature characteristics of the horizontal and vertical surfaces and the area of the cooling area of liquid nitrogen and liquid carbon dioxide were studied by changing the injection parameters such as the injection flow rate and the caliber.The temperature rise after the injection was compared and analyzed under the same conditions.The results show that: the phase change occurs rapidly when the liquid CO₂ is injected into the loose coal body and the temperature of the coal body is changed.The temperature of the coal body is reduced to-79.1 oC,and as the pressure flow rate and caliber increase,the diffusion rate is obviously accelerated,the range is larger and the cooling effect is more obvious.Compared with the liquid nitrogen,the low temperature region injected into the liquid CO₂ shows a significant lag in the temperature recovery process.Therefore,from the point of view of persistent cooling,the effect of carbon dioxide on the cooling of high temperature loose coal is better than that of liquid nitrogen.Then,the change characteristics of the index gas and spontaneous combustion parameters during coal spontaneous combustion under different CO₂ concentrations were analyzed by the experiment of temperature rise.The inhibition ability of CO₂ to coal spontaneous combustion was significantly enhanced with the increase of CO₂ concentration.